It is without controversy that the number of autism diagnoses being made is on the rise. In 1991 there were about 6 cases per 10,000 births, and in 2001 there were about 42. This number continues to rise at about the same rate.

The cause of this rise, however, is very controversial. There are basically two schools of thought: 1 – that true autism rates are on the rise, and 2 – that the measured rise is an artifact of increased surveillance and a broadening of the definition. I wrote previously about this very controversy, in which I concluded that the expanded diagnosis hypothesis is much better supported by the evidence.

Now, a new study published last week in the journal Epidemiology is being presented by proponents of the epidemic hypothesis as support for their view. A closer look, however, reveals that this study does not support the epidemic hypothesis and adds little to the overall literature on this question.(more…)